Silicon dioxide nano-particles with larger particle size as well as preparation method and application of silicon dioxide nano-particles

Abstract

The invention discloses a large-particle-size silicon dioxide nanoparticle and a preparation method and application thereof.The large-particle-size silicon dioxide nanoparticle is 50-500 nm in particle size and is synthesized by evenly mixing tetraethoxysilane, ethyl alcohol, water and NH3.H2O and then stirring the mixture at the room temperature, and the large-particle-size silicon dioxide nanoparticle and a heavy alkylbenzene sulfonate surfactant are mixed and stirred to be applied to development of medium-permeability oil reservoirs. And the crude oil recovery rate can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of underground energy mining, and more specifically to a relatively large-size silicon dioxide nanoparticle and a preparation method and application thereof. Background Art

[0002] In recent years, nanofluids prepared with silica nanoparticles have attracted extensive attention from petroleum scientists and researchers because of their low cost and availability, and their ability to significantly increase oil recovery at lower concentrations.

[0003] In low permeability reservoirs, the pore throat size between rock particles is small, and nanoparticles with larger particle sizes are easy to block the pore throat, reducing the permeability of the reservoir, while nanoparticles with smaller particle sizes can better fill the pore space of the reservoir and reduce the resistance of fluid flow, thereby improving the recovery rate of low permeability reservoirs. In medium permeability reservoirs, the pore throat size between rock particles is larger, and nanoparticles with smaller particle sizes cannot fill the pore space of the reservoir well. Too low flow resistance makes the nanofluid have no time to fully interact with the reservoir and is displaced. Therefore, nanoparticles with larger particle sizes are more suitable for the development of medium permeability reservoirs.

[0004] However, due to the small size of nanoparticles, most researchers focus on the synthesis of small-size (less than 50nm) silica nanoparticles and their application in low-permeability reservoirs. Few people have studied the ability of larger-size (greater than 50nm) silica nanoparticles to improve the recovery rate of medium-permeability reservoirs. In addition, since the surface of the synthesized silica nanoparticles has hydroxyl functional groups, they are negatively charged. The large amount of cations contained in the formation water will neutralize the negative charge on the surface of the silica nanoparticles, resulting in a decrease in the Zeta potential of the silica nanoparticles, which reduces the electrostatic repulsion between the silica nanoparticles and causes the agglomeration and precipitation of the silica nanoparticles, greatly reducing the stability of the silica nanoparticles and severely limiting their development. Summary of the invention

[0005] In view of this, the present invention proposes a method for synthesizing silicon dioxide nanoparticles with a relatively large particle size and an application thereof in medium permeability reservoirs.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] First, the present invention provides a method for preparing silicon dioxide nanoparticles with a relatively large particle size, comprising the following steps:

[0008] Ethyl orthosilicate, ethanol, water and NH3·H2O are mixed and stirred at room temperature for 4-10 hours, and then centrifuged to obtain a precipitate, which is washed to obtain pure silicon dioxide nanoparticles with a larger particle size.

[0009] Preferably, the volume ratio of tetraethyl orthosilicate, ethanol, water and NH3·H2O is (0.1-5):(2-40):(0.5-10):(0.5-5).

[0010] Preferably, the stirring reaction speed is 600-1500r / min.

[0011] Preferably, the precipitate is washed with distilled water for ≥ 3 times.

[0012] The present invention also provides silicon dioxide nanoparticles with a larger particle size prepared by the method described in the above technical solution.

[0013] Preferably, the larger silica nanoparticles have a particle size of 50-500 nm.

[0014] The present invention also claims protection for the use of larger-sized silica nanoparticles prepared by the method described in the above technical solution or the larger-sized silica nanoparticles in preparing displacement fluids for improving the recovery rate of medium-permeability oil reservoirs.

[0015] Preferably, the application process comprises the following steps:

[0016] The simulated formation water at the application site is added with heavy alkylbenzene sulfonate to prepare a heavy alkylbenzene sulfonate solution with a mass fraction of 0.1%-0.5%, and then 0.01%-0.3% of the larger silica nanoparticles are added thereto, and then ultrasonically mixed to form a uniform and stable silica nanofluid.

[0017] Since the nanoparticles have poor salt resistance and cannot work under formation water conditions, heavy alkylbenzene sulfonate surfactants commonly used in oil fields are selected and mixed with synthesized silica nanoparticles. Based on the nucleophilic substitution reaction between the two, a large number of heavy alkylbenzene sulfonate surfactant molecules are bonded to the surface of the silica nanoparticles. Due to the steric hindrance between the heavy alkylbenzene sulfonate surfactant molecules, the probability of precipitation due to collision between the silica nanoparticles is suppressed, thereby greatly enhancing the stability of the nanosystem.

[0018] The present invention also claims protection for the silicon dioxide nanofluid prepared in the application process.

[0019] The present invention also claims protection for the application of the silicon dioxide nanofluid in improving the recovery rate of medium permeability oil reservoirs.

[0020] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a silicon dioxide nanoparticle with a larger particle size and a preparation method and application thereof, which has the following beneficial effects:

[0021] The invention adopts a simple and efficient method to synthesize relatively large-size spherical silicon dioxide nanoparticles with a size between 50 and 500 nm. During the application process, the silicon dioxide nanoparticles are modified by heavy alkylbenzene sulfonate. Based on the nucleophilic substitution reaction (the sulfur atom in the sulfonic acid group acts as a nucleophilic agent to attack the oxygen atom in the hydroxyl group and lose a hydrogen ion to form surface-modified nanoparticles with sulfonate groups), a large number of heavy alkylbenzene sulfonate surfactant molecules are bonded to the surface of the silicon dioxide nanoparticles through chemical reaction. Due to the steric hindrance between the bonded surfactant molecules, the probability of precipitation due to collision between the silicon dioxide nanoparticles is suppressed, thereby greatly enhancing the stability of the nano system. The nanofluid prepared by the silicon dioxide nanoparticles and the heavy alkylbenzene sulfonate surfactant has a better ability to improve the wettability of the reservoir, a higher recovery rate than water flooding and surfactant flooding, and an ability to improve the development effect of medium-permeability oil reservoirs. The synthesis method of the invention is simple, short in cycle, low in cost, and good in repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 The particle size distribution of silicon dioxide nanoparticles synthesized for Example 1 was ~150 nm;

[0024] Figure 2 The particle size distribution of silicon dioxide nanoparticles synthesized for Example 2 was ~350 nm;

[0025] Figure 3 The particle size changes of the silicon dioxide nanoparticles and nanofluids of ∼150 nm in Example 3;

[0026] Figure 4 The particle size changes of the silicon dioxide nanoparticles and nanofluids of ∼350 nm in Example 4;

[0027] Figure 5 This is a diagram of the displacement experiment of Example 5. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] 5 mL of ethanol, 5 mL of water, 0.5 mL of NH3·H2O, and 1 mL of TEOS were mixed and stirred at 900 r / min for 5 h to synthesize silica nanoparticles with a particle size of ~150 nm. The particle size distribution is as follows Figure 1 shown.

[0031] Example 2

[0032] 10 mL of ethanol, 1 mL of water, 1 mL of NH3·H2O, and 1 mL of TEOS were mixed and stirred at 900 r / min for 5 h to synthesize silica nanoparticles with a particle size of ~350 nm. The particle size distribution is as follows Figure 2 shown.

[0033] Example 3

[0034] The ~150nm silica nanoparticles synthesized in Example 1 were added to simulated formation water and 0.1% sodium heavy alkylbenzene sulfonate (HABS) solution prepared with simulated formation water, respectively, so that the mass fraction of ~150nm silica nanoparticles in the solution was 0.05%, and placed under reservoir temperature conditions (50°C), and the changes in particle size of the two were tested to investigate their stability. The ion composition of the formation water is shown in Table 1, and the experimental particle size changes are shown in Table 1. Figure 3 As shown in the figure, pure ~150nm silica nanoparticles are very unstable in formation water, and the particle size increases sharply, while the nanofluid (HABS@150Si) formed under the existence of HABS is very stable, and after 30 days, it can still basically maintain the original particle size.

[0035] Table 1 Ion composition in formation water

[0036] ion <![CDATA[K + +That + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Ca 2+ ]]> <![CDATA[Cl － ]]> <![CDATA[SO4 2－ ]]> <![CDATA[HCO3 － ]]> <![CDATA[CO3 2－ ]]> Total mg / L 3300 31 244 5171 18 1172 80 10016

[0037] Example 4

[0038] The 0.1% sodium heavy alkylbenzene sulfonate (HABS) solution prepared with simulated formation water and the 350nm silicon dioxide nanoparticles synthesized in Example 2 were added to make the mass fraction of the 350nm silicon dioxide nanoparticles in the solution 0.05%. The solution was placed at 50°C and the change of particle size was tested to investigate its stability. The ion composition of the formation water is shown in Table 1. The particle size change in the experiment is shown in Table 1. Figure 4 As shown in the figure, pure ~350nm silica nanoparticles are very unstable in formation water, and the particle size increases sharply, while the nanofluid (HABS@350Si) formed under the existence of HABS is very stable, and after 30 days, it can still basically maintain the original particle size.

[0039] Example 5

[0040] The gas permeability is 200×10 -3 μm 2 Core (size: ), vacuum saturated with simulated formation water (the ion composition of the simulated formation water is shown in Table 1) and then saturated with crude oil to determine the pore volume (PV) of the core. Then, the core was placed under 50°C reservoir conditions for aging for 24 hours, and a core displacement experiment was performed. The displacement scheme was: 1PV formation water drive + 0.5PV chemical drive (HABS drive / HABS@150Si nanofluid drive / HABS@350Si nanofluid drive) + 1PV subsequent water drive. The recovery results are shown in Figure 5 It can be seen that nanofluid flooding has a significant improvement over formation water flooding and HABS heavy alkylbenzene sulfonate surfactant flooding, which shows that HABS@150Si nanofluid and HABS@350Si nanofluid can further improve the recovery of medium permeability reservoirs.

[0041] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will comply with the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing silicon dioxide nanoparticles with a relatively large particle size, characterized in that: The following steps are involved: Ethyl orthosilicate, ethanol, water and NH3·H2O are mixed and stirred at room temperature for 4-10 hours, and then centrifuged to obtain a precipitate, which is washed to obtain pure silicon dioxide nanoparticles with a larger particle size.

2. The method for preparing silicon dioxide nanoparticles with a larger particle size according to claim 1, characterized in that: The volume ratio of tetraethyl orthosilicate, ethanol, water and NH3·H2O is (0.1-5):(2-40):(0.5-10):(0.5-5).

3. The method for preparing silicon dioxide nanoparticles with a larger particle size according to claim 1, characterized in that: The stirring reaction speed is 600-1500r / min.

4. The method for preparing silicon dioxide nanoparticles with a larger particle size according to claim 1, characterized in that: The precipitate was washed with distilled water for ≥ 3 times.

5. Silicon dioxide nanoparticles with a larger particle size prepared by the method according to any one of claims 1 to 4.

6. The silicon dioxide nanoparticles with a larger particle size according to claim 5, characterized in that: The larger silica nanoparticles have a particle size of 50-500 nm.

7. Use of the relatively large-sized silica nanoparticles prepared by the method according to any one of claims 1 to 4 or the relatively large-sized silica nanoparticles according to any one of claims 5 to 6 in preparing displacement fluids for improving the recovery rate of medium-permeability oil reservoirs.

8. The use according to claim 7, characterized in that: The following steps are involved: The simulated formation water at the application site is added with heavy alkylbenzene sulfonate to prepare a heavy alkylbenzene sulfonate solution with a mass fraction of 0.1%-0.5%, and then 0.01%-0.3% of the larger silica nanoparticles are added thereto, and then ultrasonically mixed to form a uniform and stable silica nanofluid.

9. A silicon dioxide nanofluid prepared by the application of claim 8.

10. Use of the silicon dioxide nanofluid according to claim 9 in improving the recovery rate of medium permeability oil reservoirs.

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